There are many algorithms available to control operation of electric motors. Field-Oriented Control (FOC) is one such algorithm that provides an excellent control methodology for driving a motor very efficiently and it provides great dynamic load torque response. However, at high speeds FOC may be less powerful if current shunts are used to measure phase currents as some power is lost due to max duty cycle limitations associated with current sampling. Voltage-frequency (V/Hz) control is another available control algorithm. V/Hz control is advantageous under certain circumstances as it does not monitor phase currents and thus power is not limited at high speeds, thereby allowing more power delivery.
In a washing machine environment, a desire to establish efficient operation suggests that it is important to keep currents and temperatures low during agitate cycles but recognizes that the use of high power is necessary for reaching top speeds. Normally these different operational modes are mutually exclusive.
There are parameters associated with many different devices that represent options of particular importance to consumers that are generally referred to as CTQs (critical to quality). In view of theses concerns with prior washing machine control systems, it would be advantageous to develop methodologies for operating washing machines that allows a washing machine motor to deliver multiple CTQ's including high efficiency and high power despite their generally mutually exclusive nature.